Primary hepatitis A virus infection in developing countries: decline of maternal antibodies and time of infection.

In developing countries, HAV seems to be responsible for a widespread, inapparent and protective infection during early childhood. This report emphasizes early infection and its relationship to protection by passive immunity from maternal antibody in a highly endemic area such as Somalia. Our result show that HAV infection in Somalia primarily occurs during the first 4 years of life (4 months to 4 years). Cases are infrequent in the first 3 months due to passive immunity secondary to maternal antibody (cord-blood and colostrum anti-HAV). As the level of protection declines, the rate of acute infection rises as determined by the presence of IgM-specific anti-HAV